设施菜地温室气体交换与氮淋失相互关系及调控机制

Greenhouse gases(GHGs) emissions and nitrogen(N) leaching are the most important issues of contemporary environmental safety. Quantifying GHGs emissions and N leaching and searching for appropriate mitigation measures have become a relatively hot issue for the sustainable development of China's agriculture. As the key link of carbon and nitrogen cycles, GHGs exchange and N leaching always happen together in arable soils and have complex multiple relationships, such as conflicting relations, associated relations, etc. More researches have studied the single GHG exchange rules, but the studies on the relationship between GHGs exchange and N leaching are still very scarce, so that it is difficult to clarify the controlling mechanism of carbon and nitrogen and hence restricting the establishment of related mitigation policies. Aiming at the greenhouse vegetables system, which lack of attention and is disturbed intensively by human input of carbon, nitrogen and water, this project uses the method of combining field observation with process-based model, explores the rules of GHGs exchange between atmospheric and greenhouse vegetables as well as the key processes of N leaching, analyzes the linkage relationships between not only GHGs, but also GHGs and N leaching, and verifies and perfects carbon and nitrogen cycle process-based model (DNDC model) according to the measured data, and finally reveals the comprehensive controlling mechanism on carbon and nitrogen, so as to provide the scientific method and technology decision support for optimizing carbon and nitrogen management in greenhouse vegetables system.

有效削减农田生态系统温室气体排放和控制氮淋失是我国农业可持续发展的迫切需要。地气温室气体交换与氮淋失作为农田生态系统碳氮循环的关键环节，总是相互伴随发生并呈复杂的多重关系，如消涨关系、协同关系等。针对农田温室气体交换规律前人的研究已经比较充分，但同时涉及温室气体交换与氮淋失相互关系的研究仍十分匮乏，以致难以阐明碳氮综合调控机制，制约了相关调控政策的建立。本项目以受到碳、氮、水输入人为高强度干预的设施菜地为研究对象，通过田间观测与过程模型相结合的方法，探明设施菜地-大气间主要温室气体交换规律和氮淋失的关键过程，剖析温室气体之间以及温室气体与氮淋失之间的联动关系，并根据实测数据验证和完善碳氮循环的机理过程模型，据此揭示碳氮综合调控机制，以期为设施蔬菜碳氮优化管理决策提供科学依据和技术支撑。

有效削减农田生态系统温室气体排放和控制氮淋失是我国农业可持续发展的迫切需要。设施菜地具有施肥量高、灌溉量大且频繁等特点，不仅水肥资源利用率低，而且会造成大量温室气体（N2O）排放和硝态氮淋失。因此本研究以京郊典型设施菜地黄瓜-芹菜种植模式为例，通过田间观测与模型相结合的方法，探明了设施菜地主要温室气体N2O排放规律和氮淋失的特征，剖析了N2O与氮淋失之间的联动关系，并根据实测数据验证和完善了水氮运移过程模型EU-Rotate_N，据此定量评价了水氮综合调控机制，为设施蔬菜碳氮优化管理决策提供了科学依据和技术支撑。主要研究结果如下：.（1）设施蔬菜地N2O排放具有明显的季节变化特征，基肥施用后N2O排放峰持续10-15天，追肥+灌水事件后土壤N2O排放呈现出一段短而急促的排放峰，持续时间为3-4天。常规施肥处理下N2O年平均排放总量为27.38±2.46kg N hm-2。土壤无机氮含量、土壤湿度和土壤温度是影响N2O排放的重要因素。.（2）设施蔬菜地每次施肥或者灌溉之后均观测到氮素的淋失现象，表明氮素淋溶与施氮量和灌水量密切相关。整个生长季常规施肥处理氮素淋溶量最大，达到195.38 kg N hm-2，对照处理为58.45 kg N hm-2，氮素淋失占到施氮量的12.61%。在灌溉施肥量大的黄瓜生长前期，N2O排放和NO3--N淋溶之间呈协同效应，即N2O排放通量随着NO3--N淋溶量的增加而呈现增加的趋势，但在黄瓜生长后期，N2O排放通量较小，N2O排放和NO3--N淋溶之间的没有明显的相互关系。.（3）针对水氮运移管理模型-EU-Rotate_N，利用田间观测到的作物产量、不同土层土壤含水量、不同土层硝态氮含量、N2O排放通量等水氮运移关键过程对模型进行了验证，结果表明模型不经内部参数调整就能较好地模拟了这些过程，模型模拟结果可以接受。.（4）利用模型定量分析表明，作物产量和施肥量或灌溉量之间呈极显著的线性相关关系，当施氮量达到310 kg N或灌溉量300mm时，作物产量达到最大值，随后施氮量或灌溉量的增加黄瓜的产量不再增加，但此时氮淋失量随着氮肥投入的增加或灌溉量的增加迅速增加，而N2O排放和灌溉量没有明显的相关关系，仅随氮肥用量的增加而迅速增加。对于设施菜地种植方式下，水肥综合调控能在保持作物产量的条件下，减少氮素淋失和N2O排放量，提高氮肥利用率。